Historic Bentonite Mine Reclamation  (Wyoming)
PHC-REC returned to the test plot site to monitor vegetative growth in August of 1999 after a six month growth period.  In the VAM test plot area, an excellent stand of vegetative growth was observed.
Problem:
Bentonite mining has been conducted in the Osage, Wyoming area for decades.  The abandoned bentonite mines that are reclaimed under the AML program were typically mined using the “strip mine” technique. Soil materials above the bentonite layer were removed and stockpiled elsewhere to allow access to the bentonite.  The bentonite layer was then mined to, or just below, groundwater levels so that dewatering was not required.  Upon completion of removing the bentonite layer, a pit and stockpiled overburden, bentonitic shale, and cleanings were left.  Topsoil or suitable coversoils are practically non-existent at these sites.  

The limiting factors for sustainable vegetation at these sites are soil salinity (ESP levels above 15%), soil acidity (low pH levels), drought, high air and soil temperatures, and lack of nutrient enriched soils (i.e., topsoil).  To account for these limiting factors, the typical AML soil amendment procedures for bentonite reclamation includes incorporating soil amendments (calcium chloride, gypsum, and agricultural lime), wood waste, and fertilizer.    The cost of these amendments is usually 30% or more of the total construction costs.  
 
Objective:
In the spring of 1999, PHC-REC established a six-acre demonstration plot within an abandoned bentonite pit area near Osage, Wyoming (northeast corner of the state).  The purpose of the demonstration plot was to allow the Wyoming Abandoned Mine Lands (AML) Program the opportunity to evaluate the benefits of using mycorrhizal fungi compared to the traditional AML soil amendment procedures used in their bentonite reclamation projects.    A portion of the site was treated in the traditional AML soil amendment procedure.
After a two year period, PHC-REC again returned to the site to monitor the vegetative establishment at the demonstration plot.  In the VAM test plot area, the vegetative growth of the desired plant species was very apparent and displayed sustained growth and vigor.

 
PHC-REC Natural Systems Solutions:

Steer manure (soil amendment) was applied at a rate of 38 wet tons per acre (equivalent to 20 dry tons per acre);
The site was ripped to a minimum depth of 16 inches using a dozer;
Fertilizer was applied at a rate of 40 pounds of available nitrogen per acre;
The site was disked to incorporate the fertilizer and loosen the soils; and
Pelletized VAM was applied at a rate of 20 liters per acre, pits were constructed, and the site seeded in one pass using an agricultural pitter; the seed types were annual and perennial species applied at 28 pounds (PLS) per acre.  
In addition to the PHC-REC demonstration plot, a portion of the site was treated by following the traditional AML soil amendment procedure.
 
Results:
The Test Plot comparison showed that the VAM treatment method resulted in far superior vegetative growth than the traditional AML treatment procedure.  In addition, he cost per acre of using the pelletized VAM in conjunction with the manure amendment was 33% lower than the cost of using traditional AML soil amendments. These significant cost savings were realized by using the VAM product, obtaining the manure from a nearby source, and from the decreased need of heavy machinery during the agronomic activities.
Additional Information:  One invasive type plant species, kosha, was observed in the plot area.  Because annual species were planted, the invasion species will establish themselves before and after the annual species germination period (once a year).  As this germination pattern continues and the new annual species become established in the area, the invasion species will no longer be able to stay established due to competition.